Martin et al, U.S. Pat. No. 4,228,050, discloses a complex molding composition for the compression molding of high density information records such as CEDs. This composition, in essence, comprises a thermoplastic resin, preferably a vinyl chloride-based polymer or copolymer, and sufficient finely divided conductive carbon black to provide capacitive playback of discs prepared therefrom. Typically, such compositions have a bulk resistivity of below about 500 ohm-cm at 900 mHz. The composition disclosed by Martin et al. additionally contains both liquid and solid additives such as stabilizers, lubricants, plasticizers, processing aids and the like. In addition to the function of these ingredients in the formulation, e.g. as a lubricant, the selection of each required consideration of their stability during the processing and molding of the formulation and the possibility of reactions among any two or more ingredients and/or their degradation products.
It will be readily appreciated that there are many possibilities for reactions among a large formulation such as disclosed by Martin et al. It would be advantageous to significantly reduce the number and quantity of ingredients in the Martin et al. formulation thereby reducing the potential reactions, particularly in the heat and pressure of the molding process. In accordance with the invention, there is provided an improved formulation for CEDs which contains fewer ingredients and which additionally possesses other advantages such as avoiding the need for a conventional washing step after pressing.